Slurry preheater



March 12, 1957 N. E. ANDERSEN SLURRY PREHEATER Filed April 20, 1956 FIG.

INVENTOR 2M W ATTORNEYS 2,784,499 SLURRY PREHEATER Niels EdvardAndersen, Copenhagen-valby, Denmark,

assignorto F. L. Smitlth & C01, New York, N. Y., a corporation of NewJersey Application April 20, 1956, Serial No. 579,471 4 Claims. (CI.34-54 Thisinvention relates to apparatus for heating raw material slurryby means of hot gases preliminary to a final heating operation, as, forexample, the burning of the slurry in the wet process of cementmanufacture. More particularly, the invention is concerned with a novelslurry heating apparatus, in which the heating operation iscontrollable, so that, despite substantial variations in the temperatureor the amount of the heating gases, overheating of the 'slurry withresultant excessive drying of the slurry and clogging of the apparatusare avoided. The new slurry heating apparatus may be constructed as aunit separate and apart from the apparams, in which the final heatingoperation is performed, or, when the final apparatus is a rotary kiln,the slurry heating apparatus may be formed as part of the kiln.

The apparatus of the invention includes a tubular shell mounted forrotation with its axis horizontal or approximately so and means areprovided for feeding slurry into the shell at one end and for receivingslurry discharged at the other endof the shell and supplying hot gasesto the shell. The interior of the shell is subdivided by partition meansforming at least one chamber, which contains a charge of loose bodiesand through which the gases and slurry pass in opposite directions. Thepartition means are soconstructed that only part of the gases 'flowc'ountercurreiit tothe slurry through the compartment, while theremainder of the gases is by-passed around the chamber. The by-pass maybe of such size that the quantity er gases passing in contact with theslurry in the chamber will not cause excessive drying of the slurry,regardless of the quantity of gases supplied to the apparatus, but, ifpreferred, the by-pass may be adjustable and may be varied in size inaccordance with variations in the temperature of the gases beingsupplied to the apparatus.

For a better understanding of the invention, reference may be made tothe accompanying drawing, in which:

Fig. l is a vertical longitudinal sectional view of one form ofapparatus embodying the invention;

Fig. 2 is a sectional view on the line 22 of Fig. 1;

Fig. 3 is :a view in side elevation with parts broken away of a rotarykiln provided with a slurry preheater section of the invention; and

Fig. 4 is a sectional view on the line 4-4 of Fig. 3.

The slurry preheater of Fig. 1 includes a tubular shell provided withlive rings 11 and supported for rotation with its axis inclined to thehorizontal on rollers 12, on which the rings run. The upper end of theshell extends into a hood 13 having an outlet duct 14 for leading awaythe hot gases and the slurry is fed into the shell through a pipe 15extending through the hood and into the upper end of the shell. Thelower end of the shell extends into a duct 16, which conducts hot gasesfrom a furnace, kiln, etc., into the shell and receives the slurrydischarged from the shell, the slurry being led away through a pipe 17.

The interior of the shell is divided by partition means into acompartment 18 open at the discharge end of the shell and a compartment19 open at the feed end of the shell, the compartments being longer thanhal'f the length of the shell and overlapping lengthwise of the shell.The compartments are closed at their upper and lower ends, respectively,by end walls 20 and 21, which are connected by a pair of spaced parallelside walls "ice 22, 23 lying on opposite sides of the shell axis. The

side walls extend through diametrical openings in the wall of the shelland the parts of the side walls outside the shell are connected bysections of the end walls. The side and end walls thus form a chamber 24having extensions lying outside the shell and the extensions are closedby walls 25. The side walls 22, 23 have apertured sect-ions 22a, 22b,23a, 23b, respectively, lying inside the shell and adjacent the shelland the sections 22a, etc., may be advantageously formed of grids. Thechamber contains a charge of loose bodies sufficient to cover both gridsin at least one wall in any angular position of the shell.

In the operation of the apparatus, slurry is fed into compartments 19through pipe 15 and is prevented by end wall 21 from escaping from thecompartment. As the shell rotates 90 from the position shown in Fig. 2,the grid 23a in wall 23 enters the pool S of slurry in the bottom ofcompartment 19 and the slurry flows through the grid into chamber 24,where the slurry coats the loose bodies and takes up heat from them. Asthe shell rotates another 90", the end of the chamber 24, which haspassed through the slurry, rises, so that the chamber lies horizontaland the slurry flows from the chamber through grids 22a, 22b into thecompartment 18. As the rotation of the shell continues, the slurry flowsinto chamber 24 from compartment 19, when the chamber has one endpassing through the pool of slurry, and the slurry flows from thechamber through the grids in side wall 22 into compartment 18, when bothgrids are out of the pool. During the shell rotation, the hot gasesentering the compartment 18 flow into the chamber 24 through the gridsin wall 2'2 and pass across the chamber and escape through the grids inwall 23 into compartment 19, from which they esca e through the hood 13.In their travel through e chainbet, the gases give up heat to the loosebodies 'aiid the slurry thereon.

Under ordinary conditions, the slurry supplied to the apparatus has atemperature of 20 C. and the apparatus is of such dimensions that theslurry is heated to about C. without being substantially dried. However,if the quantity of hot gases supplied to the shell or their temperatureis increased during operation, the slurry may lose so large a part ofits moisture while passing through chamber 24, that the slurry willadhere to the loose bodies and tend to clog the chamber. In order toavoid such excessive drying of the slurry, the end wall 20 is providedwith :a gas by-pass port 27 through Which part of the gases enteringcompartment 18 may flow to by-pass chamber 24 and pass into compartment19. The proportion of the gases supplied to compartment 18, which flowsthrough the by-pass port, depends on the resistance to flow acrosschamber 24 otfered by the loose bodies, and, if the slurry [adheres tothe bodies and tends to clog the chamber as a result of excessivedrying, the quantity of gases by-passing the chamber and not giving upheat to the slurry increases automatically. As the charge of loosebodies does not fill chamber 24, the bodies move back and forth in thechamber as the shell rotates and such movement frees deposits of slurryfrom the bodies, so that the resistance to gas flow offered by thebodies decreases.

In the installation shown in Figs. 3 and 4, the rotary kiln 28 rotateson live rings 29 supported on rollers 30 and its lower end extends intoa hood 31, through which a burner tube 32 projects to terminate withinthe kiln. The upper end of the kiln lies within a dust chamber 33 havinga gas exhaust duct 34 and the slurry is supplied to the kiln through apipe 35 projecting through chamber 33 into the upper end of the kiln.

The kiln is provided with :a slurry preheater section 36 adjacent itsupper end and the interior of the section is subdivided by partitionsinto four compartments extending axially, of which compartments 37, 38are open at the lower end and closed at the upper end by walls 39, 40,while compartments 41, 42 are open at the upper end and closed at thelower end by walls typified by wall 43. The upper and lower end wallsare connected by spaced pairs of side walls, such as the side walls 44,45, to form four chambers 46, 47, 48 and 49 spaced 90 and having closedextensions outside the shell of the kiln section. The side walls havegrids, such as grids 44a, 45a,'lying within and close to the wall of thekiln shell and the chambers are partly filled by charges 50 of loosebodies.

The upper end wall 39 has a gas by-pass port 51, the size of which maybe varied by a sliding damper 52 movable across the opening by areversible motor 53 driving a screw, 54, which engages the damper,through a speed reducer 55. The motor is supplied with current throughcontact rings 56 encircling the kiln shell and it is controlled by adevice 57 mounted on the kiln shell and controlled in turn bytemperature-responsive elements 58, 59 mounted at intervals along thekiln shell downward from section 36. The upper end wall has a similargas by-pass port 60 with a damper 61 similar to damper 52 and similarlyoperable by a motor 62 receiving current from rings 56 and controlled bythe device 57.

In the operation of the kiln 28, part of the hot gases passing upwardthrough the kiln flow through the chlambers 46, 47, 48 and 49 to give upheat to the loose bodies therein and the remainder of the gases by-passthe chambers and escape into the dust chamber 33. Initially, the dampers52, 61 are set, so that the gases flowing through the chambers heat theslurry to the desired temperature without excessively drying it, but, ifthe temperature of the kiln rises, the temperature-responsive elements58, 59 act through the control device 57 to cause motors 53, 62 to movethe dampers 52, 61 to increase the opening of the by-pass ports. In likemanner, a decrease in kiln temperature results in a decrease in theby-pass port opening. The'heating effect of the gases on the slurry isthus controlled, so that clogging of the slurry pre-heater as a resultof excessive drying of the slurry is avoided.

I claim:

1. Apparatus for heating slurry by means of gases, which comprises atubular shell mounted for rotation with its axis approximatelyhorizontal, means for feeding slurry into the shell at one end, meansfor receiving slurry discharged from the other end of the shell andsupplying hot gases to the shell at the discharge end, partition meanswithin the shell dividing its interior into at least two compartmentsoverlapping lengthwise of the shell and open at opposite ends of theshell, the partition means including end walls transverse to the shellaxis and closing opposite ends of the compartments and at least one pairof spaced parallel side walls lying on opposite sides of the shell axisand connecting the end walls, the side walls having iapertured sectionswithin the shell and adjacent its wall and the side and end wallsdefining a chamber and extending through at least one opening throughthe shell wall to provide an extension of the chamber, a wall closingthe end of the chamber extension, a charge of loose bodies partlyfilling the r chamber, and a gas by-pass port in the end wall closingthe end of one compartment at the feed end of the shell.

2. The slurry heating apparatus of claim 1, in which a movable closurefor the gas escape port is mounted on the end wall .at the feed end ofthe shell.

3. The slurry heating apparatus of claim 2 in which the movable closureis adjusted relative to the port by a motor and means responsive to thetemperature of the gases entering the shell control the operation of themotor.

4. An inclined rotary kiln provided with the slurry heating apparatus ofclaim 3 with the shell forming a section of the kiln at its upper endand receiving hot gases directly from the kiln, in which the meanscontrolling the motor include a thermo-responsive element mounted on thekiln wall downward from the shell.

References Cited in the file of this patent UNITED STATES PATENTS554,509 Henze Feb. 11, 1896 2,231,249 Brown Feb. 11, 1941 2,525,535Erisman et al. Oct. 10, 1950 2,610,115 Lykken Sept. 9, 1952

